Sudden fatigue as a result of glycogen depletion from not having taken in enough nutrition.

An abrupt rapping sound, as from an impact of a hard object against wood.

“I heard a knock on my door.”

A sharp impact.

“He took a knock on the head.”

Criticism.

To strike for admittance; to rap upon, as a door.

To criticize verbally; to denigrate; to undervalue.

“Don’t knock it until you’ve tried it.”

To kick a ball towards another player; to pass.